1. Field of the Invention
The present invention relates to an apparatus and method for facilitating handling pipe and handling pipe strings particularly, but not exclusively, to an elevator for handling pipe on drilling rigs. The pipe may be a single section, stand or string of drill pipe, a single section, stand or string of casing, tubular, premium tubular, drill collars or pipe incorporating a well tool.
2. Description of Related Art
In the drilling, completion and work over of a borehole in the oil, gas, water and geothermal industries pipes are run into and out of a borehole. Such an operation is sometimes referred to as “tripping in” for moving pipes down into a borehole and “tripping out” for moving pipes up and out of a borehole. Each of these operations requires pipes to be moved around a drilling rig. Accordingly, there are many problems associated with the handling and logistics of pipe handling of a drilling rig especially in the interconnecting, disconnecting, and storing of pipes on an oil drilling platform without interrupting the drilling process.
The types of pipes which need to be moved around a drilling rig comprise drill pipes, drill collars, casings, tubing, perforated tubing, liners, liner hanger tools, packers, well cleaning tools etc.
During a drilling operation on a conventional oil drilling platform, when the drill bit has penetrated such a distance into a borehole that only a small part of the drill string extends upwards from the upper surface of the drill floor, the drilling operation is stopped, and a new tubular drill string section is moved from a storage site or rack positioned outside the drill floor and connected to the upper end of the drill string. Once the new section is connected, the drilling operation may be continued. Normally, the length of the drill string sections is 30 feet or about 9 m (or a double or triple multiple thereof). Each time the drill bit has penetrated further into the underground, the drilling operation is usually stopped and a further drill string section (or stand) is added.
Many prior art drilling systems have a rotary drive, and/or a top drive, a supportive rig floor, a derrick extending vertically above said rig floor, and a travelling block which can be raised and lowered within the derrick. During drilling operations, such rig equipment is often used to insert and, in some cases remove, tubular goods from a well. Drill bits and/or other equipment are frequently lowered into a well and manipulated within a tubular drill pipe. Once a well has been drilled to a desired depth, large diameter pipe called casing is often installed in the wellbore and cemented in place in order to provide structural integrity to the well and to isolate down hole formations from one another.
Current systems for moving pipes on and around a drilling rig incorporate an elevator arranged on the end of a line hanging over a pulley wheel or travelling block hung from a derrick of the drilling rig or from bails of a top drive. The other end of the line is wound round a winch. The elevator generally comprises a pair of hinged semicircular segments, a latch and a safety mechanism to ensure the latch is closed properly. Such an elevator is sold by BJVarco under the trade name “BX Elevator”(™).
The pipe lies horizontally on a “catwalk” or on an inclined ramp or conveyor and is lifted manually clear of the surface on which it lies or the end of the pipe is exposed over a ledge. The segments of the elevator are closed about the body of the drill pipe and the latch is closed and the safety mechanism, usually a split pin is pushed into position to ensure the latch is properly closed and will not allow the latch to be opened until the split pin is removed. The elevator loosely fits around the body of the pipe such that the elevator can slide there along until the elevator abuts an upset in the pipe or a collar threaded to an end of the pipe. Drill pipe comprises an upset known as a “box” in which a female threaded end is located, alternatively an end of the pipe is threaded on to which is threaded a collar of larger outer diameter, which form a shoulder. The winch is activated to lift the elevator and the pipe hanging there from clear of the rig floor to facilitate movement of the pipe on and around the drilling rig. A roughneck is then able to swing the pipe to another location, usually for stabbing into a string of pipe already in the well or located in a mouse hole. One particular use is to facilitate movement of the drill pipe from the pipe storage areas to the well centre and the storage area close to the well centre known as the “fingerboard”. This method is used in tripping-in operations. The elevator is then used to hold the entire weight of the pipe string whilst the slips in the platform, known as a spider, are released. The pipe string is rotated and lowered into the well and then the slips in the spider are engaged with the pipe and the elevator released.
The BJ Varco “BX hydraulically actuated elevator” is able to orient the throat of the elevator between a position to engage a vertical pipe to a position to engage a horizontal pipe and engaging a pipe lying at any angle therebetween. The elevator comprises segment in the form of hinged doors. The doors on a large elevator, which must be closed around the pipe, may weigh several hundred pounds. An elevator with doors needs clearance for the doors to swing in an arc under the pipe being engaged. The pipe has to be elevated, or clearance otherwise provided, for swinging doors.
Many prior art elevators are of a “non-slip” variety. The non-slip variety are especially suited to handle pipe which does not have an upset, although may also be used with pipes which have upsets. These pipes are known as “flush”, “near flush” or “smooth walled” pipes. The non-slip elevator is provided with jaws with non-slip teeth move into engagement with the pipe, which prevents the pipe from slipping. Thus smooth walled pipe may be moved with such an elevator. The non-slip elevators have generally been constructed with doors (generally, one or two) which open to allow the insertion or removal of the pipe; doors which traditionally are heavy, slow in operation, difficult to handle and can present a considerable safety hazard to the operator. The balance point of such an elevator can change when the doors are open, thus creating handling problems and adding danger to the operator. Especially with very heavy pipes, for example, large casing, the pipe is initially in a horizontal position, laying in place on or near the floor beneath a derrick, and the hinged door elevator is lowered near the point of attachment to the pipe. The derrick personnel then are required to open the heavy door or doors, which may weigh several hundred pounds, to allow the elevator to be placed over the tubular. Because the door or doors must close around the tubular, the tubular end around which the elevator is located is often above the derrick floor.
Often there is idle time in which no actual drilling takes place. In view of the fact that the investment made in a drilling rig is very high even a relatively small reduction of the idle time is significant.
One solution commonly used to reduce the idle time on drilling rigs is to assemble two drill pipe sections, known as “singles”, each having a length of about 10 m into a 20 m stand, known as a “double”, placing the singles in a mouse hole adjacent to the drilling opening and connecting the singles by using air tuggers and spinning wrenches while the drilling operations proceeds.
One exemplary system and apparatus for such offline stand building is described in U.S. Pat. No. 4,850,439, the disclosure of which is incorporated herein by reference. However, although these conventional offline stand building systems do create significant efficiencies in the drilling process, they generally utilize many complex pieces of equipment, such as, hoists and multi-purpose pipe handling machines that result in a system which is complicated, costly, and requires significant ongoing maintenance.
Tubulars such as casing, drill pipe or other pipe are typically installed in a number of sections of roughly equal length. These pipe sections are typically installed one at a time, and screwed together or otherwise joined end-to-end to make a continuous length of pipe. In order to start the process of inserting pipe in a well, a first joint of pipe is lowered into the wellbore at the rig floor, and suspended in place using a set of “lower slips”. Such lower slips are often wedge-shaped dies which can be inserted between the outer surface of said pie and the bowl-like inner profile of the rotary table. Such lower slips hold the weight of the pipe and suspend the pipe in the well. Although such lower slips can be automated, in many applications such lower slips are manually inserted and removed by rig personnel.
To install pipe into a well, a first joint of pipe is generally inserted into a well and positioned so that the top of said joint of pipe is located a few feet above the rig floor. A rig crew or a pipe handling machine grabs a second joint of pipe, lifts the second joint of pipe vertically into the derrick, positions the second joint above the first joint which was previously run into the well, and “stabs” a male threaded end, known as a “pin-end” at the bottom of said second joint into a female threaded end known as a “box-end” at the top of the first joint. The second joint is then rotated in order to mate the threaded connections of the two joints together. Then an elevator attached to the travelling block in the rig derrick is typically lowered over the top of the second (i.e., upper) joint of pipe. Such elevators have a central bore which is aligned with the uppermost end of the joint of pipe. The pipe is received within the central bore of the elevator. Once the elevator has been lowered over the pipe a desired distance, slips within such elevators can be activated to latch or grip around the outer surface of said joint pipe. Depending on the length of the second joint of pipe, this can often occur 12 m (40 feet) or more above the rig floor.
Upon proper latching and engagement of the elevator slips around the body of the pipe, the travelling block and elevator is raised to take weight off of the lower slips. The lower slips can then be removed. Once the lower slips are removed, the entire weight of the pipe string is suspended from the elevator slips. The pipe can then be lowered into the well by lowering the traveling block. After the second or upper joint of pipe is lowered a sufficient distance into the well, the lower slips are again inserted in place near the rig floor.
The process is repeated until the desired length of pipe (i.e., the desired number of joints of pipes) is inserted into the wellbore. This same process can be utilized for many different types and sizes of pipe whether small diameter drill pipe or large diameter casing. The entire weight of the pipe can be held or suspended by the elevators and by the elevator slips. This pipe can be very heavy, especially when many joints of large diameter and/or heavy-wall casing are being run into a well.
Accordingly, it is important that the elevator slips be properly latched around the uppermost section of pipe in the derrick to ensure that the pipe remains securely positioned within the elevators. If the pipe is not properly secured within the elevators, it is possible that the pipe drop or fall out of the elevators, causing damage to the rig or the well, or injury to rig personnel. Incorporated fully herein by reference are U.S. Pat. Nos. 6,626,238 B2; 6,073,699; 5,909,768; 5,84,647; 5,791,410; 4,676,312; 4,604,724; 4,269,554; 3,882,377; 6,494,273; 6,568,479; 6,536,520 B1; and 6,679,333 B2.
U.S. Pat. No. 6,073,699 discloses an elevator for lifting wellbore tubulars, the elevator having a pair of hinged doors, the doors interlocking with the use of a locking pin to prevent the elevator from opening.